1. Field of the Invention
The present invention relates to a support device for a support base that supports a movable die and to a die-clamping unit for use in, for example, an injection molding machine that forms molded products by injecting molten resin into injection-molding dies.
2. Description of the Related Art
FIG. 19 shows an example of a die-clamping unit for forming molded products by injecting molten resin into injection-molding dies. The die-clamping unit includes a frame a being used as a foundation. A stationary platen c having a stationary die b mounted thereto is provided to the frame a. In addition, the die-clamping unit has a movable platen e which can advance toward and recede from the stationary platen c through tie bars d. A movable die f is mounted to the movable platen e. The movable die f is capable of advancing toward and receding from the stationary die b.
A pair of left and right linear guides g are provided to the frame a. The movable platen e is supported to the linear guides g linearly movably through a movable-die support member h. Further, a pair of left and right die-opening/closing hydraulic cylinders i are disposed along the linear guides g, respectively. A rod j of the die-opening/closing hydraulic cylinders i is coupled to both right and left side portions of the movable platen e. In the event of die-closing operation, the movable platen e is moved by using the die-opening/closing hydraulic cylinders i to the side of the stationary platen c, and thereby, die surfaces of the stationary die b and the movable die f are joined together.
In addition, hydraulic die-clamping cylinders (not shown) are provided in an interior portion of the stationary platen c. A proximal end portion of the tie bar d has a piston portion (not shown). The piston portion is enclosed in the hydraulic die-clamping cylinder. Inner spacing of the hydraulic die-clamping cylinder is separated by the piston portion of the tie bar d into two chambers, namely, a die-clamping side chamber and a die-releasing side chamber.
Further, the injection molding machine includes half-nuts k on a back surface of the movable platen e. Each of the half-nuts k is engaged with an engagement portion of the tie bar d via opening/closing means (not shown). The movable platen e and the tie bar d are secured together through the engagement of the half-nut k with the tie bar d.
In a state where the movable platen e and the tie bar d are secured together, when a pressure oil is introduced into the die-clamping side chamber of the hydraulic die-clamping cylinder, the stationary die b and the movable die f are “die-clamped” (“clamped,” hereafter) with respect to each other via the tie bar d.
The movable-die support member h is mounted linearly movably along the linear guides g. The movable-die support member h has a longitudinal direction in a die-opening/closing direction of the movable platen e. Accordingly, with the moment against the tilt of the movable platen e being received, die-opening/closing operation can be performed with parallelism being maintained.
In the die-clamping event, however, when the movable die f and the stationary die b are clamped by a large force being exerted by the hydraulic die-clamping cylinder (not shown) on the movable platen e, an outer peripheral edge of the movable platen e is deformed toward the side of the stationary platen c. In addition, an outer peripheral edge of the stationary platen c is deformed toward the side of the movable platen e.
More specifically, either in a side view or plan view, the stationary platen c and the movable platen e are individually deformed substantially into circularly arcuate shapes. Consequently, a problem arises in that the sliding resistance between the linear guides g and the movable-die support member h is increased.
Particularly, a growing demand is made for reduction of the sliding resistance in the event of employing a hybrid injection molding machine that drives a movable platen in accordance with a combination of a servomotor and ball screws. Therefore, conventionally, various attempts have been made for the development of technical devices.
For example, Jpn. Pat. Appln. KOKAI Publications No. 2002-154146 and No. 2002-225101 each disclose a die-clamping unit incorporating technical devices made to reduce the sliding resistance between a linear guide and a movable-die support member.
A hybrid injection molding machine described in each of Jpn. Pat. Appln. KOKAI Publications No. 2002-154146 and No. 2002-225101 includes a disc spring in a mounting portion of a nut portion of a ball screw and a movable die plate (corresponding to the movable platen described in the present invention). Accordingly, the disc spring is deflected even when the mounting portion of movable die plate is tilted, so that a bending force can be prevented from acting on screw portion of the ball screw through the nut portion.
In addition, Jpn. Pat. Appln. KOKAI Publication No. 2002-327826 discloses a die-clamping unit wherein a nut portion of a ball screw is supported by a bracket having a spherical body. In the die-clamping unit, even when a mounting portion of a movable die plate (corresponding to the movable platen described in the present invention) is tilted, the spherical body is rotated. Thereby, a bending force can be prevented from acting on the screw portion of the ball screw through the nut portion.
In addition, Jpn. Pat. Appln. KOKAI Publication No. 2003-071894 and Jpn. UM Appln. KOKOKU Publication No. 4-38936 each discloses a die-clamping unit including an elastic member provided between a movable platen and a support member to absorb a load acting on the support member. In the die-clamping unit, a component such as a coil spring or a disc spring is used for the elastic member provided for load absorption. The provision of the elastic member enables the load absorption without regulating the deformation of the movable platen.
In addition, Jpn. Pat. Appln. KOKAI Publication No. 2003-266503 discloses a die-clamping unit including a platen support member that slides along linear guides. A movable platen and the platen support member are rotatably intercoupled through a coupling member. Accordingly, in the die-clamping unit, even when a deformation has occurred in the movable platen, the deformation is not transmitted to the linear guides.
Further, Jpn. Pat. Appln. KOKAI Publication No. 2004-330449 discloses a unit including a deformation absorbing mechanism that absorbs deformation of the movable platen between a movable platen and linear guides. Thereby, even when a deformation has occurred in the movable platen, the deformation is not transmitted to the linear guides.
However, in each of the units disclosed in Jpn. Pat. Appln. KOKAI Publications No. 2002-154146, No. 2002-225101, and No. 2002-327826, the structure of the ball screw is very complex. In each of the units disclosed in Jpn. Pat. Appln. KOKAI Publication No. 2003-071894 and Jpn. UM Appln. KOKOKU Publication No. 04-38936, while a deformation of the movable platen in a front-rear direction can be absorbed, a deformation of the movable platen in a left-right direction cannot be absorbed.